A 375-million-year old fish uncovered in the Canadian Arctic a decade ago keeps on giving.

Scientists reported Monday that the hind end of the extinct creature, known as Tiktaalik roseae, has revealed a “key link” in the evolution of fins to feet.

Tiktaalik had strong, mobile hind fins that it may have used to walk on as it slithered around shallow water and mudflats, say paleontologists.

They say Tiktaalik’s large pelvic bones indicate the evolution of “four-wheel drive” locomotion occurred much sooner than believed.

“It looks like this shift actually began to happen in fish, not in limbed animals,” team leader Neil Shubin, at the University of Chicago, says in a summary of the findings.

Shubin and his colleagues found Tiktaalik in a rich fossil bed on southern Ellesmere Island in 2004. They like to describe the fossilized creature as one of evolutionary biology’s greatest discoveries in recent decades because it provides a rare glimpse into the time when marine species were evolving into four-legged land creatures.

The U.S. scientists said in their report Monday that they have agreed to eventually return Tiktaalik to Canada where it will be curated by the Canadian Museum of Nature. But Shubin and his colleagues are still busy mining the fossils, which they wrapped in plaster on Ellesmere and hauled back to Chicago.

A 375-million-year old fish fossil uncovered in the Canadian Arctic has revealed a key link in the evolution of fins to feet. Here, Ted Daeschler holds the fossil.

Along with their science report Monday in the Proceedings of the National Academy of Science, a three-part TV series starring Shubin and Tiktaalik is due to air on PBS in April.

Tiktaalik has been making headlines for years based on the scientists’ analysis of the front half of the creature, which looked like a cross between a fish and crocodile with its broad flat head and sharp teeth. Monday’s study deals with the hind end of the creatures, which grew up to three metres long.

It says Tiktaalik’s pelvis turns out to be much bigger then expected, with a prominent ball and socket hip joint, which would have been connected by powerful muscles to a mobile femur bone.

“This is an amazing pelvis, particularly the hip socket, which is very different from anything that we knew of in the lineage leading up to limbed vertebrates,” co-author Edward Daeschler said in a summary of the findings.

The scientists report that Tiktaalik had a combination of primitive and advanced pelvis features and likely used its hind fins like a paddle. “But it’s possible it could walk with them as well,” Shubin says in the release.

And “it’s clear that the emphasis on hind appendages and pelvic-propelled locomotion is a trend that began in fish, and was later exaggerated during the origin of tetrapods (four legged creatures),” he says.

Margaret's work covering science - and science controversies - has taken her to the Arctic to see the effects of global warming, to Cape Canaveral for space launches and into Ottawa's paper labyrinth ... read moreto reveal how the Canadian government has been muzzling scientists.View author's profile